1. Technical Field
This invention relates to a method of transmitting data on an ISDN subscriber line with a data channel and two or more voice- or data-carrying channels using the data channel, a line termination for an exchange, with devices for terminating at least one ISDN subscriber line, an exchange with a line termination, with devices for terminating at least one ISDN subscriber line, a network termination for a data terminal, for connection to an ISDN subscriber line, and a data terminal with a network termination for connection to an ISDN subscriber line.
2. Discussion of Related Art
Present-day ISDN subscriber lines have either a 16-kb/sxe2x80x2 data channel, the so-called D channel, and two 64-kb/.voice- and data-carrying channels (2B+D), the so-called B channels, or a 64-kb/s data channel and 30 64-kb/s voice- and data-carrying channels(30B+D). The access structures are then referred to as basic access and primary access, respectively, with the D channels being referred to as D16 and D64 channels, respectively. Analogously, the B channels are sometimes referred to as B64 channels. Besides the two aforementioned cases, the abbreviation 2B+D is known.
The D channels are used primarily for signaling between the exchange and the subscriber terminal or private branch exchange. Capacity not used by a D channel can be used for data connections.
It is therefore possible to either carry data calls in the D channel or use one or more B channels for such calls. The contents of the data calls carried in D channels on the subscriber lines are combined in the network with other data calls and transferred on B channels or through a separate data network.
Those data calls which are usually carried in D channels generally have a burstlike character, which means that a larger data volume occasionally occurs for short periods of time, while no or a very small data volume occurs between those periods. If these data calls are actually carried in the D channel, the latter will be sufficient for such calls on the whole, but long waiting times may occasionally result for the user. If, however, such a data call is carried in a B channel, substantially shorter waiting times result for the user, but this channel is utilized uneconomically and is blocked for other tasks.
However, there are also other data calls, particularly those which are time-critical and are adapted for transmission over a B channel, for which these considerations do not apply and which must in any case be sent on a B channel. As a rule, this is determined by the subscriber that originates the call.
The object of the invention is to permit more effective utilization of a subscriber line for data calls which do not have to be carried in a B channel for other reasons.
In accord with a first aspect of the invention, a method of transmitting data on an ISDN subscriber line having a data channel and two or more voice- or data-carrying channels using the data channel; is characterized in that on receipt of each connection request, a check is made to determine whether the desired connection can be or is to be established as a data connection, that said connection is established via the data channel, that a further check is made to determine whether a voice- or data-carrying channel is still free, that the capacity of said channel is added to the connection via the data channel, that provision is made for continuously monitoring whether a voice- or data- carrying channel occupied by the data connection is requested for another connection or whether such a channel hitherto needed for another connection is no longer needed therefor, that a voice- or data-carrying channel requested by another connection and occupied by the data connection is made available for the requested connection, that the capacity of a channel no longer needed by another connection is added to the data connection, and that for the transmission of data over the data connection, the respective total available capacity is used.
According to a second aspect of the invention, a line termination for an exchange, comprising devices for terminating at least one ISDN subscriber line having a data channel and two or more voice- or data-carrying channels, is characterized in that the line termination further comprises means for checking upon receipt of each connection request whether the desired connection can be or is to be established as a data connection, for establishing said connection via the data channel, for checking whether a voice- or data-carrying channel is still free, for adding the capacity of said channel to the connection via the data channel, for continuously monitoring whether a voice- or data-carrying channel occupied by the data connection is requested for another connection or whether such a channel hitherto needed for another connection is no longer needed, for making a voice- or data-carrying channel requested by another connection and occupied by the data connection available for the requested connection, for adding the capacity of a channel no longer needed by another connection to the data connection, and for using the respective total available capacity for the transmission of data over the data connection.
According to a third aspect of the invention, an exchange with a line termination comprising devices for terminating at least one ISDN subscriber line having a data channel and two or more voice- or data-carrying channels, is characterized in that the line termination further comprises means for checking upon receipt of each connection request whether the desired connection can be or is to be established as a data connection, for establishing said connection via the data channel, for checking whether a voice- or data-carrying channel is still free, for adding the capacity of said channel to the connection via the data channel, for continuously monitoring whether a voice- or data-carrying channel occupied by the data connection is requested for another connection or whether such a channel hitherto needed for another connection is no longer needed, for making a voice- or data-carrying channel requested by another connection and occupied by the data connection available for the requested connection, for adding the capacity of a channel no longer needed by another connection to the data connection, and for using the respective total available capacity for the transmission of data over the data connection.
According to a fourth aspect of the invention, a network termination for a data terminal, for connection to an ISDN subscriber line having a data channel and two or more voice- or data-carrying channels, is characterized in that the network termination comprises means for establishing a desired connection via the data channel, for adding the capacity of a further channel to the connection via the data channel, for making a voice- or data-carrying channel requested by another connection and occupied by the data connection available for the requested connection, for adding the capacity of a channel no longer needed by another connection to the data connection, and for using the respective total available capacity for the transmission of data over the data connection.
According to a fifth aspect of the invention, a data terminal with a network termination, for connection to an ISDN subscriber line having a data channel and two or more voice- or data-carrying channels, is characterized in that the network termination comprises means for establishing a desired connection via the data channel, for adding the capacity of a further channel to the connection via the data channel, for making a voice- or data-carrying channel requested by another connection and occupied by the data connection available for the requested connection, for adding the capacity of a channel no longer needed by another connection to the data connection, and for using the respective total available capacity for the transmission of data over the data connection.
Thus,in principle, data is carried in the D channel as far as permissible, but the capacity of a B channel (or of two or more B channels) is used also as long as the latter is not occupied as such. Protocolwise, the data traffic is handled as D-channel connections.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawing.